A disruption tolerant network is a wireless multi-hop network including a plurality of communication nodes. A disruption tolerant network is also called “delay tolerant network” or “disconnect tolerant network”. Disruption/delay/disconnect Tolerant Networks are herein referred to collectively as “DTN”. In a DTN, a number of communication nodes (hereinafter referred to as “DTN nodes”) autonomously relay a message (data bundle or data packet), thereby achieving the delivery of the message from a source node to a destination node. Either or both of the source node and the destination node may belong to the DTN (i.e., DTN nodes), or belong to an external network (e.g., the Internet, a public cellular network, or a wireless local area network (LAN)). If either or both of the source node and the destination node belong to an external network, any one of the DTN nodes operates as a router or gateway that relays messages between the DTN and the external network.
The DTN is based on the premise that a temporary or intermittent loss of communication occurs due to a movement of each DTN node, shielding of radio signals by an obstacle, or the like. In other words, the DTN is based on the premise that there is no stable communication path between a source node and a destination node for at least a certain period of time. To deal with a temporary or intermittent loss of communication, each DTN node performs a store-and-forward operation. Accordingly, the DTN can also be called a store-and-forward type wireless multi-hop network. Some or all of the plurality of DTN nodes constituting the DTN may be mobile terminals having mobility. In this sense, the DTN can also be called a store-and-forward type wireless ad hoc network. It is assumed that the DTN is applied to, for example, emergency communications during a disaster, and vehicle-to-vehicle communications and road-to-vehicle communications in Intelligent Transport Systems (ITS).
Patent Literature 1 discloses an improvement in message delivery between DTN nodes. Patent Literature 2 discloses an improvement in routing in the DTN.